The overall goal of this project is to develop a manufacturing process for a recombinant WN (WN) virus subunit vaccine to prevent life-threatening WN virus infections. WN virus was isolated for the first time in North America in 1999. In less than three years, the geographical distribution of the virus expanded dramatically in the United States. A vaccine will be an important complement to other public health measures as this emerging pathogen becomes endemic in this continent. Prior work established a laboratory process for producing a recombinant WN virus envelope protein subunit vaccine. The candidate vaccine induces virus-neutralizing antibodies in mice, rabbits and horses that protect against infection in a murine model of WN virus infection. The proposed preclinical research and development activities will produce the candidate vaccine under Good Manufacturing Practice (cGMP) and Good Laboratory Practice (GLP). The objective is to produce vaccine suitable for Phase I clinical trials. Specific aims include process development, formulation with adjuvant, evaluation of safety, immunogenicity and efficacy in animal models, and preparation of an Investigational New Drug Application. This project will provide clinicians and public health officials with new means to manage WN virus outbreaks.